Turbine systems are widely utilized in fields such as power generation. For example, a conventional gas turbine system includes a compressor, a combustor, and a turbine. During operation of the turbine system, various components in the system may be subjected to high temperature flows, which can cause the components to fail. Since higher temperature flows generally result in increased performance, efficiency, and power output of the gas turbine system, the components that are subjected to high temperature flows must be cooled to allow the gas turbine system to operate at increased temperatures.
One such component that requires cooling during operation is the transition piece in the combustor. The transition piece is generally connected to the combustor liner, and provides a transition passage for hot gas flowing from the combustor liner to the turbine. Thus, the transition piece is exposed to high temperatures from the hot gas flowing therethrough, and generally requires cooling.
A typical combustor utilizes an impingement sleeve surrounding the transition piece and creating a flow path therebetween to cool the transition piece. Rows of similarly sized holes are defined in the impingement sleeve, and cooling air or other working fluids are flowed through the holes into the flow path. The working fluid flowing through the flow path may cool the transition piece.
As stated, typical impingement sleeves utilize rows of similarly sized holes for flowing working fluid therethrough. Each generally peripheral row has a plurality of identically sized, generally longitudinally symmetrical, holes. The size of the holes for a row generally decreases in the direction of the turbine. In many cases, this arrangement of cooling holes does not provide optimal cooling of the transition piece. For example, many transition pieces may include surface area portions that are particularly susceptible to excessive thermal loads. However, typical arrangements of cooling holes do not target these portions. Thus, cooling of these portions may be inadequate. Additionally, the current arrangement of cooling holes generally causes relatively large pressure drops, which may be disadvantageous for operation of the combustor and system in general.
Thus, improved impingement sleeves and methods for designing and forming impingement sleeves would be desired in the art. For example, impingement sleeves and methods that provided optimal, targeted cooling of transition pieces would be advantageous. Further, impingement sleeves and methods that reduced associated pressure drops would be advantageous.